TALLAHASSEE — Republican Gov. Rick Scott backed off his support of Medicaid expansion Monday, triggering a political backlash and giving the Florida House ammunition in its ongoing budget battle with the Senate.

Scott, who had thrown his support behind expanding Medicaid two years ago, expressed strong doubts about a government proposal to extend federally subsidized health insurance to nearly 800,000 poor Floridians.

His change of heart comes amid stalled negotiations with the U.S. Centers for Medicare and Medicaid Services (CMS) over $2.2 billion federal-state program known as the Low Income Pool, or LIP, which helps hospitals treat low-income patients.

"We still have several weeks left for budget negotiations," Scott said in a brief statement. "However, given that the federal government said they would not fund the federal LIP program to the level it is funded today, it would be hard to understand how the state could take on even more federal programs that CMS could scale back or walk away from."

Scott's office refused to elaborate on his statement, which was quickly characterized by some media outlets as a "flip-flop" and put the governor in opposition to not just the Florida Senate but a wide range of pro-business and pro-consumer groups.

His statement adds a new dynamic to an ongoing drama as the 2015 legislative session enters its sixth week. It puts the governor in line with the House in a two-against-one faceoff with the Senate at a time when the budget and most major legislation remains unresolved and tethered to the issue of Medicaid expansion.

Both chambers are controlled by Republicans. Unlike the House, however, the more moderate Senate has been insistent on expanding coverage by creating a new state-run marketplace for private health insurance. The Senate has even included $2 billion in federal Medicaid expansion money in its budget proposal.

Responding to Monday's statement, Senate President Andy Gardiner, R-Orlando, pointed out that the Senate shares many of the governor's budget priorities, including tax relief and record education funding.

"However, if our state is forced to make up the difference of $2.2 billion in hospital funding, every area of our budget will be impacted," Gardiner said.

A spokesman for the U.S. Department of Health and Human Services rejected Scott's claim that the federal government could walk away from its obligation to fund Medicaid expansion.

"The law is clear: Federal funding for Florida's Medicaid expansion covers 100 percent of the costs of newly eligible individuals through 2016 and will never fall below 90 percent," agency spokesman Ben Wakana said.

Wakana added that the federal government has "proven itself willing to work with any state interested in expanding Medicaid, and (has) consistently said that a Florida solution would reduce costs for hospitals that are typically passed on to taxpayers and expand access to quality health care for more Floridians."

Medicaid expansion has been a thorny political issue for Scott since 2013, when the federal government first offered Florida $51 billion in tax dollars to provide additional coverage to the poor. Conservatives immediately said the federal Medicaid program was too broken to grow, and linked the proposal to the politically charged Obamacare.

Scott stunned observers in February 2013 when he broke ranks with his base and endorsed expansion.

"Expanding access to Medicaid services for three years is a compassionate, common sense step forward," Scott said in 2013. "It is not the end of our work to improve health care. And it is not a white flag of surrender to government-run health care. I am committed to working every day to improve access to affordable, high-quality health care in Florida, while also protecting taxpayers and keeping our economy growing to create more jobs."

But he never put pressure on House leaders to adopt the policy. And he didn't raise the issue on the campaign trail in 2014.

Scott stopped short of specifically saying he opposed Medicaid expansion in his statement on Monday. Still, his words were quickly described as a "flip-flop" (Talking Points Memo); "walking back" (National Journal); "disgraceful Obamacare reversal" (Salon) and "change in course" (by the Associated Press, which reported it first).

The statement won praise from Americans for Prosperity Florida, an influential conservative group that opposes Medicaid expansion.

"We applaud Gov. Scott for fighting back against over-reaching federal bureaucracies and acknowledging the shortcomings of Medicaid expansion," state director Chris Hudson said Monday. "The governor has shown that he understands the need for both the federal government and Tallahassee to live within their means."

Meanwhile, advocates of expanded coverage, including a bipartisan coalition of individuals and business groups known as A Healthy Florida Works, said they were hopeful Scott would come around.

"The Florida Senate, led by President Andy Gardiner, has put forth a comprehensive, responsible approach to extending health care coverage," spokeswoman Jennifer Fennell said. "We remain optimistic that the Legislature and governor will move forward with this comprehensive plan that protects Florida families and businesses."